Split combustion in internal combustion engines of various types is known. In a typical split combustion engine, the intake and compression strokes or phases are performed in one engine cylinder, commonly referred to as the compressor, and the combustion and exhaust strokes or phases are performed in a second engine cylinder, which is commonly referred to as the combustor. The compressed air charge from the compressor is transferred to the combustor via a transfer duct. As can be appreciated, the compressed air charge is at a high pressure and typically travels through the transfer duct at supersonic speeds.
In a typical split combustion engine, combustion fuel is added to the compressed air charge either in the transfer duct or directly into the combustor. Typically, a transfer valve is positioned between the compressor cylinder and the transfer duct. The compressor piston has a phased crank-angle delay relative to the combustor cylinder, and the combustion occurs after the combustor cylinder has reached top dead center (TDC). In this way, the combustor piston can begin to move downwards while the compressor piston is still moving upwards to ensure that the combusting mixture of fuel and air in the combustor cylinder does not recirculate back into the compressor cylinder.
As can be appreciated, typical split combustion engines involve two engine cylinders in compressor/combustor pairs. Thus, an engine having an even number of cylinders will typically operate such that half of the engine's cylinders are operating as compressors, while the other half are operating as combustors, where each compressor is paired with a corresponding combustor. One drawback of typical split combustion engines is uneven heat distribution in the engine block that results from half of the engine's cylinders undergoing combustion strokes twice per engine revolution, while the other half never undergo a combustion stroke. This uneven heat distribution can cause thermal issues for all engine components involved, as well as drive different design parameters for each cylinder type and for the crankcase, which ultimately leads to increased engine complexity, additional and specialized components and development costs.